ESR is continuing its monitoring of tamiflu resistance in seasonal Influenza A (H1N1). ESR's National Influenza Centre (NIC) first identified influenza viruses resistant to oseltamivir, the active ingredient in Tamiflu, last year. It was not unexpected as other countries already have this tamiflu resistant strain.
So far this year the NIC has tested 18 samples of the seasonal AH1N1 strain for resistance. All of them were Tamiflu resistant.
Currently the Novel A H1N1 (swine flu) responds to tamiflu. However in the current pandemic resistance monitoring is crucial. Virologists internationally are watching to see what happens in the Southern Hemisphere's influenza season and whether the novel (swine flu) virus changes. Influenza viruses are notoriously unpredictable and strains change constantly.
Head of ESR's National Influenza Centre, Dr Sue Huang, said that if there was mixing of the two types of AH1N1 strains currently circulating (seasonal AH1N1 and the Novel AH1N1- swine flu) the novel virus could potentially start changing and take on resistant characteristics. Mixing would most likely occur if a person had both strains of the virus simultaneously. This is less likely to occur in people who have had the seasonal influenza vaccine as this provides protection against the tamiflu resistant seasonal AH1N1 strain.
Surveillance
ESR surveillance staff are continuing to provide essential surveillance information to the Ministry of Health's National Health Control Centre. This surveillance monitors what is happening internationally and reports on the
development of the epidemic in New Zealand through the national surveillance system EpiSurv. This also helps identify susceptible groups in the population and monitors flu symptoms being experienced so that any changes
occurring in the severity of the illness can be detected.
The annual influenza sentinel surveillance system also identified up the first cases of novel influenza disease in the community in New Zealand. Since 1991, the NIC has operated the National Sentinel GP Influenza Surveillance programme. Volunteer GPs participate by reporting influenza like illness and providing specimens for analysis during the influenza season. In each practice a swab is taken from one patient (preferably the first) seen with influenza like illness (ILI) on a Monday, Tuesday and Wednesday. These swabs are sent to either Canterbury, Auckland or ESR viral laboratories for analysis. Positive swabs are then referred to ESR for viral isolation and strain identification.
Information on ILI consultations and swabs sent from each health district is collated by ESR and reported the following week.